A COMPARISON OF SPASMOGENIC AND RELAXANT RESPONSES IN AORTAE FROM C57BL/KSJ DIABETIC MICE WITH THOSE FROM THEIR NONDIABETIC LITTER MATES/

We have investigated the responsiveness of thoracic aorta from the C57 /BL/KsJ-db/db mouse Ca model of type II diabetes) using a small-vessel myograph. The maximum tension developed in response to phenylephrine was greater in diabetic mice compared with non-diabetic (+/?) mice (2. 7 +/- 0.1 and 1.8 +/- 0.1 mN/mm, respectively). Responses to phenyleph rine were enhanced in tissues from both phenotypes when preincubated w ith L-NAME (100 mu mol/l) and after the addition of oxyhaemoglobin (3 mu mol/l), suggesting that endogenous NO release occurs in both, The m aximum relaxation to carbachol was less in db/db mice (32 +/- 4%) than in +/? mice (49 +/- 5%) whilst that to sodium nitroprusside was simil ar (>90%), However, the concentration-effect curve co both vasorelaxan ts in db/db mice lay to the right of that in the +/? mice, These resul ts suggest that the responsiveness of the vasculature is altered in th e db/db mouse, Since this mouse is a model of type II diabetes this ma y be a consequence of hyperglycaemia and/or insulin resistance.